Coated abrasives generally comprise a flexible backing upon which a binder supports a coating of abrasive particles. The abrasive particles are typically secured to the backing by a first binder, commonly referred to as a make coat. Additionally, the abrasive particles are generally oriented with their longest dimension perpendicular to the backing to provide an optimum cut rate. A second binder, commonly referred to as a size coat, is then applied over the make coat and the abrasive particles to anchor the particles to the backing.
Porous cloth, fabric and textile materials are frequently used as backings for coated abrasive articles. The make coat precursor is typically applied to the backing as a low viscosity material. In this condition, the make coat precursor can infiltrate into the interstices of the porous backing leaving an insufficient coating thickness making it difficult to bond the subsequently applied abrasive particles to the backing and, on curing, resulting in the backing becoming stiff, hard and brittle. As a result, it has become conventional to employ one or more treatment coats, such as a presize, saturant coat, backsize or a subsize coat, to seal the porous backing.
The presize, saturant coat, backsize and subsize coat typically involve thermally curable resinous adhesives, such as phenolic resins, epoxy resins, acrylate resins, acrylic latices, urethane resins, glue, starch and combinations thereof. A saturant coat saturates the cloth and fills pores, resulting in a less porous, stiffer cloth with more body. An increase in body provides an increase in strength and durability of the article. A presize coat, which is applied to the front side of the backing, may add bulk to the cloth and may improve adhesion of subsequent coatings. A backsize coat, which is applied to the back side of the backing, that is, the side opposite that to which the abrasive grains are applied, adds body to the backing and protects the yams of the cloth from wear. A subsize coat is similar to a saturation coat except that it is applied to a previously treated backing. The drawback of such a presize, saturant coat, backsize and subsize coat is that it entails added processing step(s) which increase the cost and complexity of manufacturing. Similarly, paper backings may be treated to prevent penetration of make adhesives and/or to waterproof.